The Slayers did this in the first season, when Rezo threatened to turn all the people in a town to stone if he didn't get the statue Lina stole in the first episode. To her credit, Lina was mostly just using it to get close enough to try to kill Rezo after he made his threat.
Also a bit of Forgotten Phlebotinum, as the statue in question is known to contain the Philosopher's Stone (which, in this universe, makes sorcerers much more powerful). At this point Lina is already a world class Sorceress (both she and Rezo have a color, i.e. are recognized as Archmages). She could easily have turn the people back or even prevented them from doing so, as any discrepancies in power would be clearly made up for by the Stone.
Yu-Gi-Oh! GX: Saiou threatens to let Edo fall into a Lava Pit unless Judai hands over the access key to a laser weapon in space. Judai complies to save Edo, then challenges Saiou to a duel for the fate of the world. Saiou points out what only the truly most Genre Blind would forget: the time to make a challenge is before you hand over the Plot Coupon, not after.
Also, in the first season, one of the Seven Star Assassins holds Ryo's brother hostage for his Spirit Gate Key. He was actually willing to go through with it too, until Sho said he didn't mind being sacrificed. Ryo surrendered anyway.
Yu-Gi-Oh! had quite a few of this, as well: The first season had Pegasus hold Yugi's grandpa hostage for his Millennium Puzzle, while simultaneously holding Kaiba's brother hostage for his company. The second season and Virtual Nightmare sub-arc had Kaiba's brother held hostage yet again, first for Kaiba's Egyptian God Card, then for Kaiba's own body, while Yugi had Anzu and — later — Jonouchi held hostage for his God Card and Millennium Puzzle.
Nadia: The Secret of Blue Water does this when Nadia, Marie, and King are taken hostage by Gargoyle and Jean is told to trade the Blue Water for his friends' lives.
In Death Note, Sayu Yagami is taken hostage by Mello and traded for the Death Note. Uncharacteristically, Mello takes precautions so that the Note cannot be traced by the SPK or Japanese police, but makes no attempt to kill the hostage or Souchiro (who delivered the Note) after the trade — this makes a lot more sense in the manga, where he later blackmails Souchiro for information about the police investigation.
In Tengen Toppa Gurren Lagann, a beastwoman has taken all the female cast (and Gimmy) hostage from a hot spring and projects an image of them in their cage with a mosaic over their naughty bits. In exchange for Kamina giving up control of Gurren, she offers to remove the mosaic from the display, which Kamina immediately accepts. The beastwoman keeps her word, only to reveal everyone (except, of course, Gimmy) is wearing towels, and the Gurren was stolen while he was distracted.
In Transformers Headmasters, Sixshot takes Wheelie prisoner and threatens to execute him unless he gets the secret of Fortress Maximus' sword. He was apparently willing to let Wheelie go if Fortress came up with the goods, but Wheelie was rescued by Chromedome before his full intentions were revealed.
Happens twice in Transformers: Robots In Disguise, though the first time was by accident. On the first occasion, Sky-Byte started attacking a tower just to be evil, but turned it into a hostage situation when Wedge mistook it for one. Later on, Megatron threatened to kill Wedge unless Optimus Prime handed over the O-Parts, but Sky-Byte messed it up.
Invoked and subverted in InuYasha when the Thunder Brothers kidnap Kagome. The younger one was originally going to just eat her, but she convinces them that if they do, Inuyasha will have to avenge her death... but if they don't, he will gladly give them their Shikon Jewel Shards in exchange for her safe return. (It doesn't work, but only because the older Thunder Brother gets impatient and simply attacks him for them.)
Played straight, however, in the "The Tragic Love Song of Destiny" anime special with Mistress Centipede, who attacks Kaede and attempts to take her hostage with the intent on ransoming her to Kikyo for the Shikon Jewel; fortunately, InuYasha shows up at that moment and chops Centipede into confetti before she can carry out that threat. Also subverted in that same case; though InuYasha also desires the jewel, he has no intention of holding Kaede hostage for it, preferring to take it from Kikyo in a fair fight.
In an episode of Pokémon, Buneary was captured by Team Rocket, and Pikachu can't do anything, since shocking the mecha will mean hurting Buneary (who has a crush on Pikachu). Team Rocket offers to release her, if he joins Team Rocket. Pikachu accepts, but unsurprisingly, TR doesn't release Buneary.
Ah, great. The old 'sacrifice your partner or lose the weapon' gag.
In Pokémon Special, Noland gives Guile Hideout the translated Jirachi report in order to save Anabelle's life, thus allowing Guile to nearly flood the world with a magically wished-up Kyogre.
Inverted in After War Gundam X. The antagonists have captured Garrod's companion and Love InterestTiffa, and are holding her near their newly-completed Wave Motion Gun, made out of a space colony. Garrod arrives with his own Wave Motion Gun, the colony-destroying Satellite Cannon, and demands her return or else he'll cripple their superweapon. After a demonstration on Garrod's part, the antagonist's leader realizes his best move is to send Tiffa over. As soon as she is safe next to her soon-to-be boyfriend in the Double X, Garrod blows it up anyway.
Vincent takes Sharon hostage in Pandora Hearts (and poisons her) to get Break to destroy Alice's memories he got from Cheshire in exchange for the antidote and her freedom. He does it and true to form Vincent throws the antidote off the balcony, fortunately it's saved by Echo
In an issue of Nodwick, a pair of dragons have captured a noble knight and his retinue and demand a series of powerful artifacts for his return. After the party succeeds in making the trade and the dragons leave, the now-freed knight instantly proceeds to chew them out for their stupidity in handing the wyrms the means to cause suffering to an untold number of innocents... enraging the party fighter and wizard into pummeling him senseless◊.
In Calvin & Hobbes: The Series, Dr. Brainstorm tries to hold Hobbes hostage and get Calvin's inventions in exchange for him, but due to several complications he gets Socrates instead.
Queen Of All Oni: In chapter 12, Finn (empowered by Kuro's mask) kidnaps Viper and holds her hostage in exchange for Ozeki's mask.
Crowns of the Kingdom averts this when Minnie and Daisy flee with the Serpent Crown, trusting the guys to handle themselves with the Dispirations.
Subverted in the film and literary versions of The Da Vinci Code, when Teabing has Sophia hostage and demands that Langdon hand over the cryptex, which contains the location of the Holy Grail. Knowing that Teabing's legs are crippled, Langdon throws the fragile cryptex in the air, causing Teabing to panic and fall over attempting to catch it.
Subverted in the film The Rock, where General Hummel threatens to execute a civilian hostage if Stanley Goodspeed, and John Mason don't return the guidance chips for the General's nerve-gas equipped missiles. When it looks like Goodspeed might go through with the deal, Mason crushes the chips.
Parodied in The Naked Gun 33 1/3, where Rocco has Jane held at gunpoint and Drebin is holding the bomb Rocco wants. Naturally Drebin refuses, prompting Rocco to mention Jane. Drebin then agrees, only for Jane to intersect and explain how they'd all die if Rocco got the bomb. After several different suggestions all work out in no real way where Drebin and Jane can be alive together, Drebin points out the madness and says that's he's the cop, he should have the gun, and that Rocco's the villain, and he should have the bomb. They then engage a swap, and as expected, Rocco snatches the envelope, and hands over the gun, as everyone slaps their heads at the stupidity of it.
Averted in the original RoboCop: during a attempted rape stopped midstream by the appearance of the titular hero, one of the wannabe-rapists grabs their victim, trying to use her as a meat shield. Robocop shoots the hostage taker in a VERY sensitive area, right through the woman's skirt. The other wannabe rapist surrenders rather quickly after this.
Averted in Speed where Keanu Reeves shoots the hostage (Jeff Daniels) in the leg to make him immobile to keep the hostage taker from taking him along.
In Hellboy II: The Golden Army, Prince Nuada makes such a demand of Abe Sapien. Which is strange, because Nuada's hostage is his own sister, and any injury she suffers is transmitted to him, making his threat the equivalent of holding a gun to his own head. But Abe's holding the Idiot Ball, so he complies anyway.
This was one of many issues with the Dungeons & Dragons movie. Villain takes Chick captive and demands Hero hand over MacGuffin, okay, business as usual. However, the MacGuffin in this case is a magic rod that summons and controls dragons. Critics and audience alike saw the obvious solution in that, but of course, Hero didn't.
Mortal Kombat: Annihilation. Shao Kahn threatens to kill hero Johnny Cage, and Raiden immediately threatens to respond by killing all four of Shao Kahn's greatest warriors right there on the spot. Then in a defining Idiot Ball moment, he instantly backs down from his threat. Johnny Cage pointlessly dies moments later.
Subverted in the film version of The Wizard of Oz, when the Wicked Witch of the West has Dorothy and Toto trapped in her castle. The Witch threatens to kill Toto unless Dorothy gives her the ruby slippers, and Dorothy tearfully agrees to do so, but the ruby slippers are stuck to Dorothy's feet and won't come off, something the Witch remembers the hard way when the slippers shock her.
Sneakers. Big Bad Cosmo captures Liz and threatens to kill her unless Martin Bishop gives him the box containing the decoding chip. He promises to let them go once he has the box, but double-crosses them. Luckily, Martin has a couple of aces up his sleeve.
"El Dorado". The villains capture Cole Thornton and offer to trade him for Bart Jason, the Living MacGuffin, who is in jail awaiting trial for murder.
The plot of Frantic. The wife of Harrison Ford's character disappears from their hotel room after she picks up the wrong suitcase at the airport. Once the villains realise they've grabbed the wrong person, they offer to exchange the wife for the suitcase containing the MacGuffin — Ford's character is willing but a rival faction which also wants the MacGuffin interrupts things.
Hocus Pocus. The witch has Danni. Max has the potion the witches want and that they've spent the movie in pursuit of. The witch threatens Danni if Max doesn't hand over the potion, while Max threatens to smash the bottle if Danni's hurt, to which the witch replies that she will kill Danni is he does smash it. Max Takes a Third Option: he chugs the potion himself.
Witch: Thou art a fool to give up thy life for thy sister's!
In Rise of the Guardians, after Jack rejects Pitch's offer of We Could Be Feared Together, Pitch revelas that he has Baby Tooth, and demands that Jack hands over his staff in return for her. Jack does so, at which point Pitch promptly has an 'I Lied' moment, snaps Jack's staff in two, and dumps Jack, Baby Tooth, and the staff down a crevasse.
In the NarniaSolo-Game "Return of the White Witch", it is possible to be in a position to screw up the enemies plans, having two key components the villains need to resurrect the Big Bad. Preventing this will save many, many lives; however the villains get you to give up by threatening a random baby squirrel (which seems less weak when you remember that animals are the same as people in Narnia). If you insist on the "needs of the many" route and call their bluff, Aslan steps in and forces you to submit, and your Karma Meter takes a hit. No arguing with Big Lion Jesus.
The Radix: Metzger does this to Brynstone's wife and daughter.
Much of the plot of The Dresden Files novel Small Favor revolves around this, however with the subversion that Harry and the Big Bad both know neither side intends to follow through with their end of the bargain, but keep up with the pretense because it's the most profitable course.
It is... Slightly more complicated than that. Both Harry and the Big Bad knows that the other side will try a trick. But both are sure they have a BETTER trick. Also, a very profitable course. For the Big Bad, at least.
In the Dale Brown novel Edge of Battle, Jason Richter is threatened with the lives of some children if he doesn't give up the activation command for a CID. He gives it up... and Zakharov not only lets him go, but also doesn't backstab him afterwards.
Mr. Motley makes this offer to late into Perdido Street Station: Lin's life in exchange for the slake-moths. However, the resident Satisfied Street Rat says that he's seen Motley pull this trick before, and every time, the hostage was dead before the demand was even made, because there's nothing in it for him not to kill them. It later turns out Motley actually did have a reason to keep Lin around (not that Lemuel would have had no way of knowing it), but it's still unlikely that he'd have kept his end of the bargain.
In the first book, Slank takes Molly hostage and demands the trunk of starstuff in return.
In the second book, Umbra and his crew capture Shining Pearl for the same reason. The Molluscs don't have the starstuff, though, so they end up using her to guarantee safe passage back to their ship.
In the Rainbow Magic series, the goblins try this in Leona the Unicorn Fairy's book, but it turns out to be a bluff.
Live Action TV
Subverted in Buffy the Vampire Slayer, "Choices": The Scoobies have captured the Box of Gavrok belonging to Mayor Wilkins, while Mayor Wilkins has captured Willow. The Scoobies debate the morality of destroying the box instead of giving it to the Mayor, but agree to make the trade. Wesley, however, insists on destroying the box rather than letting Wilkins have it, but Oz then proceeds to smash the pot needed for the ritual to do so to ensure that they will trade for Willow. The Mayor does not attempt to kill Willow anyway, and releases her once he has the box. The result is that Willow is safe, but the Mayor has the box.
An Averted Trope in "Bad Girls". The demon Balthazar has captured Giles and Wesley.
Wesley: Now, hold on. We can deal with this rationally. We have something you want. You have something we want. Balthazar: Hmm... A trade. Intriguing. (considers) No. Wait. Boring. Pull off his kneecaps!
Subverted and played straight in the old Doctor Who story The Daleks' Master Plan. The first time it happens, the Doctor goes for the third option and gives the Daleks a fake MacGuffin so he can get the TARDIS back. The second time this tropes plays out straight, but only because for once the Doctor's Indy Ploy didn't come off right.
Kamen Rider Ryuki has a rare example where the character actively chooses the MacGuffin over the hostage. Kagawa Hideyuki (Alternative Zero) wants to stop the war of the Kamen Riders and the bloodshed it causes. When Big Bad Kanzaki Shirou threatens to kill Kagawa's family, Kagawa lets him do it and continues to fight for the greater good. This is held against him, of course, since Kagawa is the local Straw Vulcan. (The family survives, because Kido Shinji butts in and saves them without Kagawa's knowledge.)
Kamen Rider Gaim has a subversion. Kouta's older sister Akira is kidnapped and held for ransom, but when Kouta goes to collect her, it turns out that the Bound and Gagged woman is actually Kamen Rider Marika in disguise. She proceeds to violently attack him as soon as he gets close enough to untie her wrists.
In an episode of Mighty Morphin' Power Rangers, everyone in Angel Grove is kidnapped by Rita, and the Rangers must give up their power coins (making them powerless) to have them released. They comply, but Rita doesn't hold up her end of the deal.
A subversion comes in a later episode, when the same trick is tried again. Not surprisingly, this time the villains get chocolate coins.
On NCIS, the Weatherman leaves a kidnapped, drugged little girl lying on a pressure plate, which is wired to electrocute both her and a bank of computers if she moves. Given more time, the agents might've been able to deactivate the trap without destroying the computers' crucial information; unfortunately, the girl starts to wake up and they have to snatch her off the bed fast, saving her life but forfeiting the stored data.
Once Upon a Time has Cora holding Aurora hostage in exchange for the magic compass in Emma's possession. Aurora sneers at the notion that people she just met will trade something so valuable for her, but Cora is assured that Snow and Emma's inherent goodness will cause them to fold. It ends up being moot when Hook frees Aurora though not before removing her heart, which is used to control her and lure the others into a trap.
In RoboCop: The Series Robo is forced to steal components for a prototype weapon (a heart-attack gun, yes seriously) to secure the freedom of his (ex)wife; putting him at odds with his programming and police.
In the events portrayed on Dawn of Victory, by Rhapsody, the Princess Irene is captured by evil forces, who threaten to kill her unless the Emerald Sword is surrendered to the evil king. Subverted: when the heroes arrive they are captured and made to watch while the Princess is raped to death by demons. One of the heroes escapes, sans Emerald Sword.
Sonic Adventure 2, where Eggman has Amy Rose held hostage and Sonic has the final (fake) Chaos Emerald in his possession. Eggman, however, correctly guesses the Emerald is a fake and promptly launches Sonic into space.
It gets used so often that your Karma Meter in Skies of Arcadia goes down if you actually fall for this — and Aika will instead refuse on your behalf, after calling you an idiot.
Final Fantasy IX has this. When you're trying to invade Kuja's fortress, he takes your group hostage and has half of them go off and steal a Plot Coupon from a dungeon he can't breach due to its Anti-Magic field. The other half manages to escape, but not quick enough to prevent the hero from handing the item away.
In addition, since Garnet is a magic user and Zidane isn't, the player will probably put Zidane in the party going after the plot coupon and leave Garnet in the hostage party, fulfilling the "hostage is the hero's lover" variant of this trope.
Final Fantasy Tactics: the villains try to use this scheme to push Ramza into handing over the Zodiac Stones and the Germonik Scriptures. He sees through this enough to negotiate a compromise and only hands over the Scriptures. Unfortunately, this plus the two Zodiac Stones the villains already had eventually proves to be just barely enough when push comes to shove...
In a separate instance, the villains hold Mustadio's father Besrodio captive so that they can get Mustadio's Zodiac Stone. After Mustadio tells them where it is and Ramza hands it over, the villains gloat and attack the heroes anyway. Joke's on them, however: Mustadio gave them a fake.
The very first Wild ARMs game has a Princess handing over a magic stone that will enable the villains to destroy the world; because they want to destroy her kingdom. In the Video Game RemakeAlter Code F, she gets into a hefty argument with another party member over the morality of this. Her reasoning is that the people of the city are dying now, and handing over the MacGuffin will save them, but doom the planet to a slow death, which she reasons can be averted by getting the MacGuffin back. So she wasn't entirely naive.
Happens in both Golden Sun games; the characters have been told that handing over the MacGuffin will destroy the world, yet they do so anyways. Yes, later it's revealed unlocking the MacGuffin is a good thing, but at the time, they didn't know that.
In the first game, the antagonists are holding a girl hostage and they demand the party to hand over a staff in exchange that the girl won't be harmed. The party hands the staff over and then complain to the antagonists that they are not holding up their end of the bargain, saying they would let her go. The antagonists then gleefully point out that those were their terms; they only agreed to not harm the girl.
Sa Ga 2: In a relatively unusual variant of the trope, once your characters hand over the 76 MAGI they collected, the villain releases the hostages and leaves. The door he leaves through is sealed and requires MAGI to open, so he assumes that you will never be able to reach him. He never knew about the 78th MAGI.
At one point in Clive Barker's Undying, one of the villains demands a magic stone from the main character in exchange for his friend's life. Despite his friend's protests, and despite the fact that killing the friend has seemed to be the sole goal of the villains up to this point, he hands it over. This doesn't play out so much to standards of the trope, as to how it realistically would — the baddie kills his hostage, then uses the stone to enhance his powers.
Late in Ganbare Goemon 3, the villain Shishi Jurokubei demands the Conch Shell used to summon Goemon Impact in exchange for Omitsu, the hero's Love Interest. The exchange is made without a hitch until the hostage is revealed to actually be Villainous Crossdresser Sister Bismaru, the real Omitsu having been with Jurokubei all along.
In Pokémon Ranger: Shadows of Almia your idiot rival gets himself captured by the Bad Guys and they offer him in exchange for the shiny gem you've just caught that would ruin their plans to plunge the world into everlasting darkness. Despite the rival insisting that you keep the gem because even he can see how obviously better of a decision it is, But Thou Must is in full effect and you have to make the trade no matter what.
In Tales of SymphoniaYuan holds the hero hostage to get his father, Kratos to give Yuan the Eternal Sword, with which he intended to save the world himself. It might have worked, if the Big Bad hadn't interrupted.
Used in the first Vandal Hearts; interestingly, the team is saving a known traitor.
In the first Ninja Gaiden (the NES one), Jaquio makes Ryu give him the Demon Statue that will let him summon the Ancient Demon; or else he would kill "the girl." (Irene, but Ryu at this point didn't even know her name.) Naturally the Demon is summoned, but fortunately Ryu kills the Demon anyways.
In Lost Magic, at the end of the descent from the peak of the Balance Temple, the Diva of the Twilight shows up, verbally confounds Trista, her sister, effectively making her a hostage, and then gives you the option to either give Isaac's Wand of Light to the Diva or hold on to it. You actually do get to choose in this case, although the game really wants you to give up the Wand.
In Seiken Densetsu 3, whichever villains correspond to your chosen main character will kidnap the Faerie in a bid to get the Mana Sword. In a rare twist, all of the villains keep their part of the bargain and return the Faerie unharmed.
In Epic Mickey, the Phantom Blot threatens to kill Oswald and Gus if Mickey doesn't surrender his heart. Mickey spends the rest of the game trying to stop the unleashed Blot and get his heart back.
Case 2-4 of Phoenix Wright: Ace Attorney. Shelly de Killer kidnapps Maya in order to force Phoenix to acquit Matt Engarde. Of course, Phoenix has no idea that Engarde hired de Killer to kill Juan Corrida.
In Brave Fencer Musashi after obtaining the Sky Crest, the Flatski demand Musashi to hand over the completed sword Lumina for the captive princess. Musashi hands over the sword and Flatski activated it on the crest causing the Sealed Evil in a Can to be released.
In Solatorobo, Bruno kidnaps Elh to make an exchange for Red's medallion and indirectly his life.
In Assassin's Creed: Revelations, after it becomes clear to the Big Bad that Ezio cannot be stoppedby any man or army in his quest to recover the Masyaf Keys, he instead pulls a classic "I have your girlfriend" ploy. Ezio, who is at this point weary to the bone of the constant struggle, accepts the terms but has his fellow Assassins prepare for the inevitable treachery, which gives him an opportunity to chase down the villain and recover the keys.
In Assassin's Creed III, Abstergo captures William Miles during an ill-advised solo mission to recover a Plot Coupon. Vidic then offers a trade: Desmond's father in return for the Apple of Eden. Desmond obliges, but not quite in the way that Vidic expects. It turns out that letting a man with a Lost Superweapon walk into your office is not such a great idea.
To be fair, Vidic has no way of knowing that Desmond knows how to use the Apple, since the Bleeding Effect of the Animus hasn't been explored by Abstergo much.
Near the end of Act I of Neverwinter Nights 2, the githyanki that have been periodically bothering you for the length of the chapter attack the Sunken Flagon and kidnap Shandra Jerro. Interestingly they don't demand the Plot Coupon at first because they think Shandra knows where it is. It's only after you battle your way to their inner sanctum that they bring the trope into play. Then it turns out that you have another Plot Coupon embedded in your chest, and they attack to get it.
DmC: Devil May Cry has this when Mundus stages a raid on The Order's headquarters and kidnaps Kat, then asks for Virgil in exchange. The Order counters by Dante going to Lilith's nightclub, subduing her, and offering the trade of Kat for Mundus's unborn child. Both parties agree to this exchange. But when this exchange happens, Virgil shoots Lilith in the stomach, killing both her and Mundus's unborn child, and manages to escape with Kat too, subverting the trope.
In The Cliffhanger: Edward Randy, at the end of the first age, the villain makes Randy give him the prism in exchange for the girl.
PAYDAY: The Heist does this twice in Diamond Heist. If the codes for the vault leading to the diamonds don't work, you're then told by your Voice with an Internet Connection to go find the CFO of the building and escort him to the helipad where he will be used as a bargaining tool against the CEO for the codes. Simply put, the codes, or the CFO's life. Due to the randomness of the game, sometimes the CFO himself will give up the codes and his life is spared. If the CEO refuses to negotiate, then the crew has the CFO booted out the helicopter as he crashes into the glass dome and dies on impact. The crew is then told to go find the CEO's son to use him as leverage. If it reaches that point, the CEO will always give in.
In Ctrl+Alt+Del, a corporate executive abducts Lilah to force her boyfriend Ethan to surrender the crown of Wintereenmas, as he believes this will give him control over the gaming industry. Ethan complies immediately, telling Lilah she's much more important than the crown, but the cute twist comes when the gamers rebel and reinstate Ethan as the King of Wintereenmas.
In a Youtube video called "Blaze Goes To Disneyland," there is one scene where Eggman kidnaps Cream and offers her back if Blaze gives Eggman the Chaos Emerald. Despite Cream telling Blaze not to give the Chaos Emerald... despite Blaze demanding that Eggman put Cream down right now, Eggman, being the villian he is, threatens to throw Cream into the lake, causing Blaze to give the Chaos Emerald anyway... and Eggman runs off without giving Cream back.
Ducktalez: Vegeta kidnaps Scrooge's nephews after their first fight in an attempt at getting the Lucky Dime.
Winx Club put a few twists on this when the Trix capture Stella: Bloom gave the Trix Stella's ring, which they had been trying to get for the duration of the series up to this point (5 episodes). This was in exchange for the Trix letting Stella go. The witches oblige, but in the very next episode, it turns out that the ring does not contain the power the Trix are really looking for.
The Winx would face this again in season 3, this time letting that season's Big Bad get away with a magic box in exchange for saving a guy who's interested in Aisha (Aisha is completely uninterested in him, and she doesn't know that he's her intended, but obliges anyway).
Invertedtwice on Code Lyoko: the Lyoko Warriors put Aelita in danger to force XANA to back off his attack. Good thing she's only useful to him alive.
Which makes sense, since Aelita is as textbook an example of a MacGuffin Girl as you're likely to find.
Played straight in the appropriately named episode "Ultimatum," when XANA possesses the school principal and kidnaps Yumi and Odd whom he threatens to "liquidate" should Aelita not give herself up to him in the given time frame.
Used in Transformers Animated, with the justification that the villain making the threat plans to start with the hostages and keep up the death and destruction until he finds the MacGuffin himself. Neither party intends to honor the agreement.
Used rather nastily in Armada. The hostage turned out to be The Mole. Also played straight when Megatron kidnaps Billy and Fred and holds them in exchange for the Mini-Cons.
Iron Man: Armored Adventures lampshades and justifies this trope in the season one finale when Zhang holds Pepper hostage and forces Tony and Gene to retrieve the fifth Makluan Ring for him or else he will kill Pepper. Pepper responds to this with a sarcastic 'Gee, THAT'S original'. However, this allows Pepper to get close enough to Zhang to steal back other four Makluan Rings which Zhang stole from them earlier.
In The Spectacular Spider-Man, Doctor Octopus pulls one of these when Spider-Man plays keep-away with the Applied Phlebotinum Doc Ock needs to power his Artificial Limbs. The chase leads toward Coney Island, where Octopus realizes Spidey feels obliged to save Innocent Bystanders from the resulting chaos. Exploiting this, he grabs a nearby damsel and leaves her hanging precariously from a rollercoaster to force Spider-Man to give up the power source. The damsel is actually Peter Parker's then-girlfriend (sort of) Liz Allan, though neither she nor Octopus know Spidey is Parker.
In Barbie & The Diamond Castle, Lydia forces Melody, hiding in a mirror, to show herself (and give up the location of the Diamond Castle) by ordering a mind-controlled Alexa to walk toward a pit of lava/acid. Once Melody comes out, Lydia promises to set Melody's friends free once the Diamond Castle is revealed, but as they leave, she secretly orders her pet dragon to off the other girls (who end up escaping and saving the day).
Transformers Prime: The Decepticons capture the three humans and hold them hostage in exchange for the Omega Keys, which have the ability to restore Cybertron and end the war. The Autobots give up the keys and the minute Megatron gets them, he tries to destroy all the other humans by terraforming their planet, and Optimus is forced to destroy the machine and doom their planet to the barren husk it currently is.
In Stitch! The Movie, Hamsterviel tries to bargain Jumba for the other experiments. But Lilo tries to intervene - and ends up captured herself.